Formation control



Juy i9, M49. F. A. JENKS i 2,476,393

FORMATION CONTROL Filed May 31, 1943 5 Sheets-Sheet l Fga Mom/AMR /7 I I ENVENTOR FeEDf/P/CA'. ldii-NMS BY y f3 ATmRNEY Jy w, w49.. F. A. JENKS www FORMATION CONTROL '45 ATTORNE Judy 9,1949. F, A JENKS 2,476,3@l

` FORMATION CONTROL Filed May 31, 1943 5 sheetssheet s ATTORN EY F. A. .JENKS FORMATIONl CONTROL Juiy lO, 1949.

Filed May 3l, 1943 PHASE DETECTOR GYRO VERT/CAL R m M7 mf 7 o 7 m m M E R mw m MM M9 W mf VRI o mm M m Re Lf Am a VR PII/15E 0E 75670,?

VOZ. 74 65 SUPPL Y N mw T .fm @wm m@ MM F July w, i949.

Filed May 3l, 1943 F. A. .JENKS FORMAT ION CONTROL 5 Sheets-Sheet 5 mwa VERT/CAL C2055 POINTER fla/e. REP.

l g 364 INVENTOR 372 37/ Herat-AUC A MEN/ 5 ATTORNEY pending upon .visible contact.

Patented July 19, 1949 FORMATION CONTROL Frederic A. Jenks, RockvilleCentre, N. Y., as-

signor to The Sperry Corporation, alcorporation of Delaware Application May 31,

21 Claims.

This invention relates generally to a system-for enabling a plurality of craft to maintain predetermined positions lin a formation without de- The invention relates particularly to apparatus for determining, indicating and controlling the position of each craft ina formation relative to a control or leadking craft. The embodiments of the invention herein `described are particularly applicable to formation flying and glider towing.

It is well known vthat poor visibility conditions place limitationsonformation ying. In order to avoid a possibility of collision between various craft inthe formation, andsimilarly in glider towing where one Aplane is towing a plurality of gliders, provision must be made to maintain the gliders in predetermined lateral positions relative to the towing4 craft.

Itis therefore the main object of the present invention to provide a formation control system in which relative ,positions of various craft in the formation maybe determined.

Another object of the invention is to provide indicators carried by the craft in a formation to .indicate their positions relative to a control craft.

A further object of the invention is to provide a formation control system in which the vvarious craft in a formation may determine the attitude of a control craft.

Afurtherobject .of the invention is to provide a formation -control system with automatic pilot means for maintaining craft in predetermined positions relative to a control craft.

A further object ofthe invention is to provide a control system for formation flying wherein compensation is effected for changes in the pitch and/or heading of a control craft.

Other objects and advantages of the invention will become apparent from the following specication, taken in connection with the .accompanying drawings,A wherein Fig. l is a schematic-diagram of a transmitter for a control craft which defines a reference axis.

Fig. 2 is a cross-section of the beam patterns .of the transmitter shown inFig. 1.

Fig. 3 is a schematic diagram of a receiver for use in connection with the transmitter of Figi-112i" for determining `and indicating its position relative to a control craft and also the attitude of f the control craft.

Fig. 4A is a ydiagram showing the reference axis defined by thebeam pattern of a control craft in horizontal flight.

Fig. 4B is a similar diagram ,showing the error introduced by the beam pattern du@ t0 movements of the control craft.

Fig. 5 is a schematic diagram of an indicator circnitfor use with .the receiver .VShQWll in Figand l compensated'to Azorrevct errors ldiie to move- 'ments of the leading craft.

Fig. 6 is a'scliernatic diagram of an indicator circuit similar'tofthat shown vin Fig. 5 but including additional data s 4tofthe attitude of the leading craftby connections to anovel indicator.

Fig. 7 isla schematic block `diagram of a radio controlled Vautomatic.pilottliat.may be used with thereceiver shown in'Fig. y

. Fia `81S asohematigdiaeram 0f a modied l5 form of transmitterfor deiining'a referencel axis.

Fig. ashows .tne'r-Qsitins 0f the craft in a yformation relative to lthe fbeam'patterns radiated by the transmitter shown lin Fiajs.

Fig. 10 is a schematic diagram of a receiver adapted for use in connection with .the transmitter shownin-Fig.

Fig. 1l shows ralpparatus adapted for use in glider towing f or determining the positions o f the glidersrelative tothe towing plane.

Fig. l2 lshows a simplifiedglider towing kSys tem similar to `that of 11.

The formation lcon-trol system forming vthe present inventionvinolugles atransmitter ,carried by .a control,k craft,r which may be theleading craft of the formation, that defines a reference airis for all of the .craftin-the formation. The controlled or following `crafthave receivers for de.- termining and indicating their positions Arelative .to the reference .axis denfedby the transmitter in the control craft, The. pilots of the controlled .craft manipllleiether Centres to maintain 'their respective icraft in @predetermined position relative to thereference axis of the control craft as Vshown byindioators ,in l each .of ,thecontrolled craft. Provisionrnay 1also yloe made for `using ,automatic pilots. .whereby the controlled craft are automaticalli-y` rnai-ntained in va `predetermined position. w

One arrangement for defining the reference axis of the `control l systemgis'. shown schematical- 1y inlFa 1 as aradiotransmitter kin which high .freouencyenergy is developed 'by Power osllatar Iy I and transmite@ thro-.ugh suitable wareei1des .I2 and I3 `to directional antenna ...l-v haring .a parabolic -reiecior daptedto @eline a dire@- tional beam of radianterierey. .A motor .contained ,withinllousinel .is adapted to rotate-the reflector 1.5 wh' As illustrated particularly in Fig. 1, the high frequency energy of power oscillator II is modulated by modulator I1 at short predetermined intervals during rotation of the reflector I5. Fig. 2 shows a cross-section of the modulated conical radiant energy pattern. The modulation is applied during four short intervals of each rotation of the refiector I5.

A different frequency is applied by the modulator I1 for modulating the high frequency carrier at each of the four intervals during a single revolution of the antenna I4. These frequencies, which will be referred to as f1, f2, f3 and f4, are applied by suitable conventional oscillators 2l, 22, 23 and 24, designed to generate four suitable modulating frequencies, preferably in the audio range. These oscillators are connected to une modulator l1 through a commutator system on a shaft 25 driven through insulated coupling from the motor I6. The shaft 25 makes one revolution for each revolution of the reflector I5. Four commutator discs 26, 21, 28 and 29 are carried by the shaft and small segments 3|, 32, 33 and 34 are insulated from their respective discs. The segments are displaced at 90 intervals for connecting the oscillators 2I, 22, 23 and 24 for short periods to the shaft 25. Slip ring connects the shaft 25 to modulator I1.

During each revolution of the shaft 25 the frequencies of the four oscillators are supplied for successive short periods to the modulator I1. During the intervals between modulation the four oscillators are short-circuited to a ground connection 31 by commutator discs 26, 21, 28 and 29.

When the beam pattern of the antenna I4 is at its maximum height, as shown in Fig. 2, frequency f1 of the oscillator 2I is connected through segment 3I and shaft 25 and then through slip ring 35 to modulator I1. The modulation applied to the high frequency energy of power oscillator I I has a frequency corresponding to the frequency f1 of the oscillator 2l. During the short period for which this modulating frequency is applied, the antenna I4 continues its rotation and hence produces a beam pattern such as that shown at 33 in Fig. 2. As the antenna continues its rotation, the unmodulated carrier is rotated about the longitudinal axis of the parabola I5 in conical fashion, as has been described, until the com- ?.utator segment 32 connects the shaft 25 to oscillator 22, at which time a second modulation frequency f2 is supplied to the modulator I1 and thence to the power oscillator II.

The beam pattern followed by the conical radiant energy pattern during the application of the second modulator frequency is shown at 39 in Fig, 2. In a similar manner, the oscillators 23 and 2li are connected to the modulator I1 and the modulation frequencies f3 and f4 are applied during short intervals as the radiant energy pattern of the antenna I4 continues to rotate. The beam patterns produced by these modulating frequencies f3 and f4 are shown at 4I and 42 (Fig. 2)

The axis of the motor-antenna assembly forms a reference axis for the entire formation of aircraft, and is represented by the center point of the beam patterns shown in Fig. 2. This axis is also the central axis of the conical pattern described by the energy radiated bythe antenna. Obviously, other types of antennae may be employed to produce a similar pattern. The receivers carried by the various controlled or following craft in the formation detect the energy from the antenna I4 and compare the strength of the Various modulating frequencies to determine their positions relative to the center axis of the beam patterns.

3 shows one receiver suitable for this purpose. This receiver includes antenna 43 that is connected as by a coaxial cable 45 to a receiver 46. The wave envelope of the energy detected by the receiver is supplied to an audio amplifier 41. The output of the amplifier 41 as represented by leads 48 and 49, is connected in parallel to a plurality of filters 5I, 52, 53 and 54, which are tuned to the modulation frequencies f1, f2, f3 and f4, respectively.

The outputs of the filters 5I and 53 are connected through suitable gain control devices, such as potentiometers 55 and 56, to an elevation oomparator-detector circuit 51. Since the modulating frequencies f1 and f3 are applied at the upper and lower maximum pointsvof the conical beam pattern, the strength of the signals received by the antenna 43 may be compared to determine the vertical displacement of the antenna 43 relative to the reference axis at the center of the transmitted beam patterns. The comparator-detector circuit 51 compares the amplitudes of frequencies fi and fs and produces a direct current output at leads 6I and 63 corresponding in direction and magnitude to the direction and vertical displacement of the antenna 43 relative to the reference axis of the beam pattern.

The leads 6I and 63 are connected toasuitable indicator, such as cross pointer indicator 65, that is well known in the art, to indicate whether the following plane should be directed upwardly or downwardly to maintain a predetermined posi#- tion relative to the center of the beam pattern.

If it is desired to y the controlled or following craft at a point displaced vertically relative to the center of the directional beam pattern, 'potentiometers 55 and/or 56 may be adjusted to attenuate one or the other of the frequenciesfi or f3. For example, if it is desired to fly a specie distance above the axis of the beam pattern, theaoutput of the filter 5I is reduced hypotentiometer 5-5 to attenuate the frequency f1, sothe signals supplied to the elevation comparatordetector 51 by potentiometers 55 and 56 are'eq'ual when the antenna 43 is displaced a predetermined distance above the center of the beam patterns. If the following craft is to fly Abelow the center of the beam patterns, the potentiometer '.56 is adjusted to reduce the signal corresponding to the modulating frequency f3, whereby the elevation comparator-detector 51 receives equal lsignals when the antenna 43 is positioned at a specific point below the center of the beam patterns.

The pilot in the controlled craft manipulates his controls to maintain the horizontal pointer 66 of the cross pointer indicator 55 in a central position. Horizontal pointer 56 is centrally positioned when the outputs of lters 5I and A53 for frequencies f1 and fa are equal and hence the potentials of leads 6I and 63 are equal with respect to a neutral point in the comparator-detector 51.

The outputs of filters 52 and 54 for modulating frequencies f2 and f4 are connected through potentiometers 6l and 68 to a heading comparatordetector 69. The output of the Comparator-detector 59 as represented by leads 52 and 64, is connected to controla vertical pointer 1Iv of the cross pointer indicator E5. The vertical pointer 1I moves laterally depending upon the relative voltages of the output leads of the heading com# parator-detector corresponding to the modulat- 4ing frequencies f2 land Jriwhicl'iy are supplied by potentiometers 61 and 68; The signals may be adjusted by potentiometers 61 and 68, whereby the vertical pointer 'll will "be centered when the controlled craft is displaced laterally a predetermined distance and in apredetermined direction relative to the reference axis of the beam patterns.

Once the potentiometers 55, 56 and-61, 68 are adjusted, the pilot, bymaintaining the pointers (S5-and il inthe centerfof the cross pointer vindicator 65, will automatically maintain .the following craft carrying `the antenna 133 :in a predetermined positionrelative to the'reference axis defined by the beam patterns.

Although the cross `pointer indicator .6-5 is sufficient to maintain the following craft in a predetermined position vrelativeto the reference axis defined by the transmitter carried by the control craft, it is difficult for 'the pilot to .follow maneuvers of the control craft. .An lindication of the attitude of the control craft will enable the pilot of the following or controlled craft to antcipate maneuvers of the control craft, the energy radiated by the antenna is further modulated in response to changes in the attitude of the control craft.

rThis modulation of the'energy radiated by the antenna i4 is accomplished by modulating the power oscillator il in accordance with 'signals from an attitude indicating device such as gyro vertical or artificial horizon 74, such as that described in Patent No. 2,262,245, of Moseley et al. issued November 11, 1941. Changes in attitude of the craft about the pitch axis cause pick-offs l2 and 'i3 to produce reversible phase and variable magnitude voltages corresponding .to the direction and amount of .pitch of the craft. Similarly, movements of the control craft about its roll axis cause pick-offs and 'l'to produce reversible phase and variable magnitude voltages corresponding to the direction 'and movement of the craft about the roll axis.

The pitch signals from vthe pick-offs 12'and i3 are supplied to a phase-detector 'll which produces a direct current voltagehaving a direction and magnitude corresponding to the pitching movements of the craft. This voltage controls a variable reactance 'i8 which varies Athe frequency of an oscillator 19 above and below a selected center frequency that corresponds to level flight of the craft.

The variable frequency of the oscillator i9 is coupled by a transformer 8|, having its secondary tuned by a condenser v82, to the circuit from high voltage supply source 83 to the power oscillator Il. The power oscillator may include a velocity modulated tube such as a Klystron, the frequency of which can be varied by varying the applied voltage. power oscillator Il is varied according to the variable oscillator T9, the frequency of the power oscillator is modulated by the frequency of the oscillator i9. In this manner, the frequency of the energy radiated by antenna 'I4 is modulated by a frequency that is varied according to the pitching movements of the control craft.

In a similar'manner, the reversible phase variable magnitude voltageof pick-offs15 and 16 corresponding to the rollingmovements of the f control craft is supplied'toazphase detector 83 which controls a variablezreactance 84 to adjust the frequency of an 'oscillator.85 aboveV and below a center frequency depending .upon therolling movements of the craft. Ihisiva'ryingfrequency Sincethe voltage'applied to the `:is coupled by a transf-.ormerfklph'aving its .sed- 'ondary tuned Lby a Yicondensera'il; tofithe :circuit of the high voltage :supply .isourceffatfforz the power oscillator Inl.. Thusitheifnequency lofsthe power oscillator I I dszalso fmodulated b yfa `fre.- quency depending uponl the positionf fof'. =the vcon'- trol craft relative .to itsrollaxis.

Center frequencies ifs andffsiof the; oscillators 'i9 and 85 must, of course, loe-selected` so the ranges of the modulating. frequencies will not overlap. These .frequencies :are preferably. above the audible range :in norderzto ;avold'interference with the frequencies used by modulator il?! to vdetermine the reference .axisof *.ther'control craft.

The antenna 43 of .the following .craft :.is. connected by coaxial cables il5 andi89:to-fa frequency modulation .receiver .whichnmay :include 1 sultable limiter and demodulationicircui'ts..` .The output of the receiver 90 is connectedfto arband pass amplifier 9 I which `amplifles 'the v:entire frequency range of the variable.osci1l'atorsi19'andl85. In order to segregate pitch-and rollsignals, a suitable trap may be used to `attenuatefrequencies between the frequency ranges l'of 1the modulators 'it and 85. i

The output of the fbandvpass "amplifier-9i is connected in parallel to pitchand rll discriminators 92 and 93, whichare1tunedxtothe-center frequencies f5 and ,fs of Ioscillators I9 and 85, respectively. These discriminatorcircuits'may be of any suitable-conventional designto produce a direct current output #voltage having a sense or polarity and magnitude dependent upon the deviation of the received modulatingfrequency relative to their Arespective `tunedfrequencies.

The output of `the discriminatorf92 produces signals corresponding topitch'ing ymovement-.sof the control craft which are'supplied-'by .leads 95 and 96 to a horizon repeaterfindicator 9i to control the vertical position -of a miniature airplane 98 of the indicator. The vertical displacement of the mini'aturaairplane 98 from its central position represents pitching Y' movements of the control'craft 'as determined-bythe gyro vertical 'i4 (Fig. 1).

In a similar manner, Athe output of the discriminator 93 .as Vrepresented by leads lili and |82 has a direction and magnitude *corresponding to the rolling movements of the-contro1 craft. Leads I8! and E92 are .connected to the 'horizon repeater indicator I91 vto rotate the miniature airplane 98 in a manner to Y'represent -rollin movements of the control craft;

The output lof the transmitter; 'carried -by the control craft is thus -modulated`fby-a varying frequency in accordance with its pitching and rolling movements, `as determinedby the gyro vertical '14. As shown; -the 'variable'frequencies of the modulators -'l9andf85I areutilized to frequency modulate-thecarrier. However, the variable modulating lfrequencies 'could also be used for amplitude modulationpf the carrier by making certain alterations in the transmitter and receiver circuits shownin Figs, l1- and 3. However, the result would'bersubstantially the same and an instrument' fsuch as'the lhorizon repeater 91 could' be used to indicate the attitude of the control craft.

Figs. 4A and 4Billustrateithe"introductionof certain errors infthe reference-axis as the "control or leading craft`|`|`l V`deviates-from a straight line course -to change Aits 1heading `or'relevation. As shown in'Fig. 4.A,ja'following craft fl ii2-fly+ ing :alonefthe reference axis H3 of the` lbeton pattern satisfactorily follows the leading craft during level flight. However, as the leading craft begins to change its elevation, as shown in Fig. 4B, the reference axis IIS is displaced upwardly so the following craft ||2 receives a signal on its cross pointer indicator 65 to ny upwardly. This, of course, is opposite to the action which the pilot of the following craft I|2 should take in order to follow the control craft lll. Similar errors are introduced as the leading craft ||l Abegins to change its heading. If it turns to the right, the axis H3 is displaced to the left and the following craft receives a signal to turn to the left, which is opposite to the signal it should receive. It is necessary, therefore, to compensate for the errors introduced by movements of the reference axis as the control craft begins to change its course in lateral and vertical directions.

The apparatus shown in Fig. 1 is designed to effect this compensation by closing switches H5 and H5 that are connected between vertical and lateral deviation rate devices lill .and H, and phase detectors llt and lll, which control vertical and lateral servomotors H3 and llil.

The deviation rate devices il@ and ilil may include any suitable rate measuring instrument for producing a signal corresponding to the rate of deviation of the control craft from a straight line course. Turning movements of the control craft result in a lateral deviation; hence a measurement of the rate of turn corresponds to the rate of lateral deviation. As the control craft begins to climb or dive, it changes pitch. The rate of change cf pitch corresponds to the rate of vertical devia ion, Once the control craft assumes a constant climb or dive angle, the rate of vertical deviation, or rate of change of pitch, becomes Zero.

One example of an instrument suitable for use in the device iii) and llfl for measuring vertical and lateral deviation rates is described in U. S. Patent No. 2,399,853, issued February 3, i943, to Joseph Lyman et al. This instrument produces an alternating voltage having a phase and a magnitude corresponding to the direction and rate of turn or deviation from a straight course. Such a reversible phase, variable magnitude voitage from vertical and lateral deviation rate devices lli and lill may be supplied through switches H5 and ii to phase detectors |56 and lil which control the vertical and lateral servomotors llt and H9 to adjust the beam pattern of antenna if 'vertically and laterally by an amount corresponding to the changes in attitude of the control craft.

As the craft begins to climb or glide, the voltage of the vertical deviation rate device lli? acts through the phase detector |66 to actuate motor ||8 which drives shaft |2| forming one input of a compensating differential |3l. The output of the compensating differential |35 represented by shaft 532 rotates pinion |22 which meshes with a gear |23 to drive through gearing i245 and |25 to rotate a shaft |25. A worm gear ill'l on. the shaft |25 rotates a sector |28 to adjust axis H3 of the antenna lll in a vertical direction.

When the control craft begins to turn, phase detector l l? is actuated by a voltage from the lateral deviation rate device corresponding to the rate of turn. The phase detector ||1 then energizes the lateral servornotor IES which rotates shaft |29 to drive pinion |33 that meshes with gear |34 to adjust the lateral position of the axis ||3 of the parabola l5 according t0 the rate of turn of the control craft. A shaft |36 is driven by gearing |31 from the shaft |29 to drive a, second input of the compensating differential |3| thereby preventing lateral movements of the parabola l5 about a vertical axis fro-rn causing vertical movements of the parabola.

In operation, the axis of the parabola, that is, the reference axis, is adjusted vertically and laterally according to the rate of vertical and lateral deviation of the control craft from a straight course. For example, as the control craft begins to dive, the reference axis ||3 (Fig. 4B) is gradually adjusted vertically as the rate of vertical deviation increases. Then as the control craft approaches its desired dive angle, the rate of deviation is gradually reduced and the reference axis is gradually returned to its normal position relative to the control craft.

Since the antenna is adjusted vertically in the opposite direction to the vertical deviation of the control craft as it begins to dive, the controlled craft will not receive erroneous signals to fly upwardly. As the control craft continues to move downwardly, the reference axis also moves downwardly and the controlled craft follows the reference axis. As the control craft approaches its desired dive angle, the antenna returns to its normal position.

The controlled craft will resume its normal position relative to the reference axis, and both the control craft and the controlled craft will be diving at the same angle.

Similarly in turning, the antenna is rst adjusted laterally in a direction opposite to the lateral deviation of the control craft. For example7 if the control craft turns in a clockwise direction, the antenna is adjusted in a counterclockwise direction. This avoids erroneous signals in the controlled craft. As the control craft continues turning, the reference axis moves with it in the same direction and the controlled craft follows. As the control craft straightens out on a new course, the antenna returns to its normal position and the controlled craft resumes its normal position after completing a turn substantially identical with that made by the control craft.

Although erroneous signals are eliminated by lthe apparatus described, the pilot of the controlled craft may still be supplied with an indication of the attitude of the control craft, whereby he may anticipate maneuvers which he will have to make in order to follow the control craft.

The mechanical movement of the reference axis H3 by adjusting the parabola l5 vertically and laterally is, of course, cumbersome in that considerable equipment is required to accurately control the position of the parabola. Another and preferable arrangement for compensating the erroneous signals depends upon the relative attitudes of the leading and following craft. This may be accomplished by a circuit such as that shown in Fig. 5, which is arranged to be connected to leads 6|, 62, 63 and 64 corresponding to the outputs of the comparator-detectors 51 and 69, forming the outputs of discriminators 92 and 93, respectively- The transmitter in the control craft may be the same as that shown in Fig. 1, except that the rate devices I Ill and I4 together with the related equipment for vertically and laterally moving the antenna I4 may be eliminated. This is, of course,

effectively accomplished by `opening switches |I and. I I5'. i

A gyro verticalor artificial horizon |4| is carried by the controlled craft and has. pick-offs |42 and Iswhich produce reversible phase and variable magnitude signals corresponding to movementsof vthe controlled craft about its pitch axis in a similar manner to that described in connection withthevertical gyro Hlv (Fig. 1). Pickoiis |54- and |45 produce-signals corresponding to rolling movements ofthe controlled craft. The pitching signals of pick-offs |42. and |43 are supplied to a phase detector |48. The output of the phase detector |43 is connected in series with the outputs of the discriminator 92, the elevation comparator-detector 5,1, and the control circuit for the horizontal pointer 66 of the cross.

tector |536, the other-side ofv which is connectedl to the indicator 65 that isin turn connected to the lead Si forming one of thel output leads ofA the elevation comparator-detector 5l. The circuit is completed by connecting lead 63v from the comparator-detector 5'I to lead 9.5y of the discriminator 92.

The output of-discriminator 92- corresponds to the pitching movementsof the control craft, and the output of the phase. detector |48 corresponds to pitching movements of the. controlled craft.

By properly connecting the discriminator 92 and phase detector |48 so the polarities of their outputs are in opposition,the horizontal pointer is displaced from its central position-according to the difference in` pitch of the two craft and the vertical displacement of the controlled craft relative to the referenceaxis. As long as the two craft have the same attitude, the horizontal pointer 66 will be displaced only in accordance with deviation of thev following craft from its predetermined position 7relative to the reference axis |53. Since the pitch of the control. craft is changed at the beginning of a change in. its elevation, that is, a vertical deviation from a straight course, a signal corresponding to the difference in the attitude ,of thev two craft will move the horizontal pointer 66 in a direction which will indicateto the pilot of the following craft that he should take appropriate action to .match the attitude of his craft withA that of the control craft.

The introduction of the voltage representing the .difference inthe attitudeV of the two vcraft compensates for errors introduced at the beginning of changes in elevation of the control craft iii and thus eliminates the, necessity for the mechanical control of the parabola I5 (Fig, 1). Therefore the switches I|5 and II5 are not closed when the controlledV craithas a compensation circuit such as that shown in Fig. 5.

Similarly, voltages of pickoffs |44 and |45 are supplied to a, phasel detector |52, the output of which is connected by lead |02 to the discriminator 93 and by a lead |53 to the control for the vertical pointer 1I of cross pointer indicator 65. The other side of the vertical pointer circuit is connected by lead 62 to the headingcomparatordetector 58 which is connected by lead 64 to lead I iii of discriminatorSS, ,thus forming a series circuit including the comparator-detector 69, discriminator 93, phase detector |52 and indicator 65.

Since it is, assumed that the control craft makes standard turns which the banking angle is determined by the rate of turn, the difference in the rolling movements of the two craft will represent the difference in their respective rates of turn. When the two craft are turning at the same rate and banking at the same angle, the output of phase detector |52 balances the output of discriminator 93 so the vertical pointer |I is positioned in accordance with the position ofthe control craft relative to the reference axis- II3.

As the leading craft begins to turn, the vertical pointer 'II indicates to the pilot of the following craft that he should turn in the same manner. This circuit eliminates the necessity for lateral adjustment of the parabola |5 by servo motor ||`9.

As has been described, the circuit shown in Fig. 5 provides means for4 determining the relativey attitudes of the` two craft, and means for determining the displacement of-l the followingcrafty from its predetermined rposition relative to thel reference axis. Signalscorresponding to the difference in the attitude of the two craft are usedi to compensate the .position determining means to. correct errorsv introduced by deviation from a straight line course, such as changes in heading or elevation, by the control craft.

Fig. 6 shows a circuit similar to that of Fig- 5, and in addition includes an indication of banking movements of the control craft. The circuits for controlling horizontal and vertical pointers 66 and '|I are identical with that described in connection with Fig. 5, and similar reference numerals have been used to designate the various components ofthe circuit. In addition, leads I0| and |02 are connected to control of` a novel cross pointer indicator 65 in which the background |55 for the pointers 66 and is rotated about a horizontal axis. tion of the background |55 is controlled by voltages of leads IDI and Il|2 which correspond to rolling movements of the control craft as determined by the discriminator 93. In this manner the pilot, by watching the cross pointer indicator can determine at all times what action he should take to remain in a predetermined position relative to the reference axis of the beam pattern. In addition, he is provided with indications ofthe banking angle of the control craft which should be the same as his own banking. angle. Fig. 7 illustrates an arrangement for using the receiver shown in Fig. 3 to actuate heading and' elevation controls |6I and |62 of an automatic pilot |63, such as that shown in Sperry et all Patent No. 1,992,970, issued March 5, 1935. In addition, the automatic pilot I 63 also includes means for automatically banking the craft in accordance with changes in rheading as determined by contro1 I 6| One example of a radio controlled automatic pilot which includes this automatic bank feature is disclosed in copending application Serial No.. 378,296, filed February 10, 1941 now. Patent yNo.v 2,423,336 issued July 1, 1947 in the name. of Francis L. Moseley.

Anyof the well .known automaticpilots for controlling conventional motors |65, |66 and |61 to operate rudder. |68; automatically banking by operating ailerons |69 and II I; and to control the elevation byioperating elevators |12 and I 13, may b e used. Such systems are usually provided with follow-up. connections |15, |16 and |'I'I for the motors |65, |66 and |61, respectively.

The heading control is supplied with a voltage corresponding to the voltage-.which controls the Rotavertical pointer 1| of the cross pointer indicator 65 in Fig. 5. The circuit for the heading control |5| is a series circuit including the outputs of the discriminator 93, the heading comparator-detector 69, and phase detector |48. This voltage represents the difference in the banking angles of the control craft and the controlled craft, as well as deviation of the latter from its predetermined position relative to the reference axis. Thus the heading control |6| actuates an automatic pilot to maintain the following craft in its predetermined position relative to the reference axis and also to cause it to follow turning movements of the control craft.

The elevation control 52 of the automatic pilot is connected in a series circuit including the elevation comparator-detector 51, the pitch discriminator 92 and phase detector |52. The elevation control |62 is thus controlled by voltages corresponding to the difference in pitch of the two craft and the vertical displacement of the follow-- ing craft from its predetermined position relative to the reference axis. In this manner the automatic pilotl |63 is actuated to maintain the craft in its predetermined position relative to the reference axis and also to control the attitude of the craft in accordance with the attitude of the control craft.

A different arrangement for utilizing a radio beam to dene a reference axis for the formation is illustrated in Fig. 8. The transmitter shown in Fig. 8 includes a pair of antennae |8| and |82 having cylindrical parabolic reflectors |83 and |84 designed to provide fanshaped directional beam patterns. Cylindrical parabola |83 is arranged so the radiation pattern of antenna |8| has a narrow lateral dimension and a comparatively wide vertical dimension. The fan-shaped beam of antenna |82 is rotated through 90 so its narrow dimension is in a vertical direction and its wide dimension in a lateral direction.

The beam pattern of antenna |8| is swept laterally by oscillating wave guide |85 which supports the antenna. Oscillation of the wave guide |85 in a horizontal plane is accomplished by a motor |86 which drives through suitable gearing |81 to rotate a shaft |88 which is geared to a disc |89 having a lever |9| eccentrically mounted thereon and connected to the wave guide |85. The motor |80 is driven at a speed selected to oscillate the wave guide |85 and the antenna |8| at their natural frequency, so the fan-shaped beam is harmonically oscillated laterally through a selected angle as shown in Fig. 9. The beam from the antenna |8| may have a pattern such as that shown at |93 in Fig. 9 that sweeps through an angle 94 at the rear of the control craft l The fan-shaped beam of antenna |82 is swept through a path at 90 to the path through which the antenna |8| is moved. The shaft |88 drives through disc |95 and crank arm |95 to oscillate Wave guide |91 at its natural frequency and sweep the antenna |82 is a vertical direction. Considering the beam patterns of the antennae |8| and |82 as vertical and lateral planes of radiant energy, it will be apparent that the sweeping motion of the antennae moves the two planes of energy in lateral and vertical directions, respectively.

The fan-shaped beams of the two antennae are used to define a reference axis by modulating the high frequency energy in accordance with their angular positions relative to the longitudinal axis of the control craft A power oscillator 20| supplies high frequency energy through wave guide 202 to branch wave guides 203 and 204 that are connected to the wave guides and |91 for the antennae |8| and |82, respectively. The high frequency energy from the power oscillator is supplied alternately to the two antennae by a switch in the form of a disc 205 which rotates through the wave guides 203 and 204 and has a semi-circular slot 206 adapted to permit the high frequency energy to continue along the wave guides 203 and 204 during alternate halves of each revolution of the disc 205. The disc 205 is driven in synchronism with the oscillation of the antennae by motor |86 which drives through gear 201 and shaft 208 to rotate the switching disc 205.

The slot 206 is so positioned that each of the antennae is supplied with energy during the sweep of its fanning movement in one direction but cut off during its return sweep. Since the antennae sweep synchronously, the energy is supplied alternately during their respective sweeping movements. Suitable high frequency chokes 2H and 252 may be formed in the wave guides 203 and 204 to prevent leakage of energy around the disc 205.

One manner of modulating the fan-shaped beams of antennae |8| and |82 as they are swept laterally and vertically relative to the longitudinal axis of the control craft, is by varying the frequency of the power oscillator 20| in accordance with sweeping movements of the antennae. This may be accomplished in the following manner.

A shaft 208 drives through gearing 2|3, shaft 2M, and gearing 2|5, to rotate shaft 2|| synchronously with fanning movements of the antennae. Shaft 2| 6 drives through gearing 211 to rotate shaft 2 i8, which in turn rotates a rotary plate 2|9 of a condenser 220 having a stationary plate 22|. The plates of the condenser 220 may be connected in parallel with the main tuning condenser of an oscillator 228, whereby the frequency of the oscillator 228 is varied slightly on either side of its normal frequency f7 as the condenser plate 2.1.9 is rotated synchronously with fanning movements of the antennae.

The shaft 2|6 also drives through gearing 222 to rotate the shaft 223, on which is mounted a rotary plate 224 of a second condenser 225 having a stationary plate 225. The plates 224 and 225 may be connected in parallel with the main tuning condenser of an oscillator 234, whereby the frequency of the oscillator is varied on each side of its normal frequency fa as the rotary plate 224 revolves.

The oscillator 228 may be coupled by a transformer 229 to the circuit including high voltage supply 232 and power oscillator 20|. The secondary of the transformer 229 may be tuned as oy condenser 23|. In this manner, the output of the power oscillator 20| is frequency modulated in accordance with the frequency of the modulating oscillator 228, and since the frequency of the modulating oscillator 228 varies in accordance with the oscillation of the antennae, the power oscillator 20| is frequency modulated by a modulating frequency which varies according to the sweeping movements of the antennae.

Similarly, the oscillator 234 is coupled as by a transformer 235, having its secondary tuned by a condenser 236, to the circuit of high voltage supply 232 of power oscillator 20 The frequency of the modulating oscillator 234 is thereby varied by rotation of condenser plate 224 in accordance with sweeping movements of the antennae.

`It is Vdesired to have: one of the modulating oscillators used for each of the antennae ISI and |82. The' modulating frequency of oscillator 228 may be applied during the period that switching disc 205 supplies energy to the antenna II and the modulation frequency of yoscillator 234 applied during the alternate half of each revolutionof the' disc v205 when the antenna |82 is connected to the ypower-oscillator The variable condensers may 'also be used to alternately cut-off the ocillators 228 and 234 synchrono'usly with operation of the high frequency switch 285 so the frequency of only one modulating oscillator is supplied to each antenna. A brush 221 may be connected to the stator plate 22|` of condenser 22|] and adapted to engage rotor plate `2I9 during one-half of each revolution. This will electively short circuit the tank circuit ofthe oscillator 228 to disrupt oscillation during sweeping movements of the antennae in one direction. When the plate-2 I becomes disengaged from the brush22, the oscillator 228 begins oscillating and its frequency varies as the rotary plate 2 I 9 is rotated. In asimilar manner a brush 233 is connected to stator plate 225 and is adapted to engage rotary plate 224 during one half of each revolution. The brushes 227 and 232 are, of

course, arranged to engage their respectiverotary platesy during alternate halves of each rotation cycle, whereby the oscillator 228 is cut-off during 2 sweeping movements of the antennae in. one di.- rection, andthe oscillator'iis cut-'off during sweeping movements of the antennae in the opposite direction.

Referring again lto Fig. 9, it maybe assumed that the fan-shapedbeam 93 has a low modu-V lating frequency when its axis corresponds to the axis 24|, a high frequency when its axis'correspends to the axis 242, and a central'frequency when in its middle position as shown. A following plane in the formation, such as the plane I2, will receive a different modulating frequency than that received by a plane |12 inra different position. The frequency received by theplanes in the formation varies according to their position relative to th-e central or reference axis of the control craft III. "I'hemodulation frequency of the beam l 93 when in its central position` as shown in Fig. 9, is the central frequency f7 of the oscillator 228. The central modulationfrequency of the beam radiated by antenna |82 is-the center frequency f6 of the oscillator 234 and defines the vertical position of the reference axis. Obvious ly, these frequencies must be chosen so they will not interfere with each otherl so the receivers in the planes in the formation will be able todistinguish between the two modulating frequency ranges. p y

A receiver suitable for use with the transmitter shown in Fig. 8 is illustrated in Fig. l0. This receiver includes an antenna Q5 connected as by Acoaxialcals-le 243i to a suitable` receiver 268, that may include conventional limiter and demodulator circuits, the output of which is connected to a band-pass amplifier 249. A heading discriminator and an elevation discriminator 252 are connected in parallelto the output of the band-pass amplifier 24S. TheV heading and elevation discriminators 255 and 2.52 are variable as shownin the drawings and may be tuned to diierent center frequencies. The output of the heading discriminator 25! is connected by leads, 2 54 and 255 to control vertical pointer 255 of cross pointer indicator 251. A Output. leads 25E and 259v ofy the elevation discriminator 252 are connected to control a horizontal pointerfZflI of' the cross pointer indicator 251.

If the head-ing discriminator 25| is tuned to the center modulating frequency of the variable oscillatorZZt the output voltage of leads 254' and 255,' relative to a'neutral point in the 4discrimiu nator, corresponds to the difference between the modulating frequency received bythe antenna 245 and the central modulating Vfrequency to which the discrimina-tor 25| is tuned. This voltage is therefore proportional to the displacement of the receiving antenna 245 relative to the reference axis defined by the fanning ybeam of antenna IBI on the control craft. For example, if lthe antenna v255i is carried by the plane II2 (Fig. 9); it `will Areceive a lower modulating frequency than the central modulating frequency. In this cas-e the voltage of the leadsv 254 and 255 relative to a'neutral'point of the discriminator y25| differs considerably and the vertical pointer 258 is `'displacedfrom its central position in a direction depending upc-n the received modulating frequency.

If it is desired to have the vertical pointer 25'6 appear in its center position when the following plane is'displ'aced laterally a predetermined distance from the vertical axis, the discriminator 25| istuned tc a frequency which it would receive at such a displacement. lFor example, the

-craft H2 (Fig. 9) would have its discriminator tuned to a frequency lower than the -center freq-u'ency'an'd the vertical pointer would bel centrally positioned when the lower frequency was-received by the antenna 2135.

The voltage ef leads 258 -and`259 forming the output'of elevation discriminator- 2512 is deter ininedby thevertical position of the antenna 245 relative tothe reference axis which determines the frequency of themodulating signal received by the antenna.

- signaL-i-nwhich case the'receiving circuit shown inFig. 10 vwould have to be modified accordingly. However,l the modulating frequency would still vary in accordance with the fanning movements of the two antenhaeand discriminators 25| and 252 wouldbeemployed vto detect lateral and vertical deviation-s of the controlled craft from its pr'edeterminedposition relativel to the reference axis denedby' thefbeams.

As showniin Fig. 8', the vertical gyro I4 may be used to modulate they output of power oscillator Ztl-'in the same manner as the vertical gyro' 'Ill (Fig. 1) Awas usedto modulate the power oscillator Il. Thus the voltage developed by picl 0iTs i2 and ".3- is supplied to the phase detector Tl to control the variable reactance 'lil which varies thefrequencyvof oscillator i9 in accordance with the pitching movements of the control craft. Similarly, pick-offs 'I5 and 'I5 supply a voltage tol the phase detector 33 which controls variable reactance to vary the frequency of oscillator in accordance with-rolling moven'ients of the controlicraft., The varying frequencies (fe and fio) lof oscillators "i9 and 85 are coupled by trans-- fornnersl and-86- to the voltage supply circuit '75 of power oscillator 26| in the samermanner as that described in connection with Fig. l. Thus the frequency of the power oscillator is also modulated by frequencies which vary according to the attitude of the control craft.

The receiver shown in Fig. 10 includes pitch and roll discriminators 265 and 266 which are tuned to center frequencies fs and fro respectively. Changes in attitude of the control craft cause the pick-offs of the gyro vertical 14 to change the frequency modulators 19 and 85 from their center frequency. These changed frequencies cause discriminators 265 and 266 to produce voltages according to the changes in attitude of the control craft.

Leads 21| and 212, representing the output of pitch discriminator 265, are connected to control vertical movements of a miniature aircraft 2l3 of the horizon repeater indicator 214. Output from leads 215 and 216 of the roll discriminator 266 control rotary movements of the miniature aircraft 213 according to the rolling movements of the control craft.

The receiver shown in Fig. 10 provides the same indications as that shown in Fig. 3, namely, the deviation of the craft from a predetermined postltion relative to the reference axis dened by the transmitter of the control craft, and also the attitude of the control craft, that is, its pitching and rolling movements. It will be apparent that the outputs of discriminators 252, 266 and 265 could be connected directly to the indicating circuits shown in Figs. 5 and 6 or to the automatic pilot circuit shown in Fig. '1.

To accomplish this, lead 254 will be connected to lead 62; lead 255 connected to lead 64; lead 258 connected to lead 6|; lead 259 connected to lead 63; lead 212 connected to lead |0|; lead 21| connected to lead |02; lead 216 connected to lead 95; and lead 215 connected to lead 96.

The discriminators 265 and 266 correspond to the discriminators 93 and 95 shown in Fig. 3. The outputs of discriminators 25| and 252 provide direct current voltages of direction and magnitude corresponding to the direction and amount of lateral and vertical displacements of the receiver relative to the reference axis. Thus, these voltages are similar to those produced by the heading and elevation comparator-detectors 69 and 51, respectively.

The two systems for defining the reference axis thus far described are adapted for use with either formation iiying aircraft or a formation of gliders towed by a single aircraft. Since a formation of gliders must be connected by a tow line to a towing aircraft, it is possible to accomplish the formation control without using radio beams to define the reference axis. The tow line itself may be used to determine deviation of the gliders from predetermined positions relative to the reference axis.

One arrangement for glider towing is shown in Fig. 11 in which a housing 30| is rigidly supported on the towing craft as by a bracket 362 and has a ball and socket joint 303 for a towing connector rod 304 adapted to attach a tow line to the towing craft. The ball and socket joint 303 provides universal movement of the connector 304 relative to the towing craft.

Since the tow line is drawn tightly, the position of the connector 304 represents the approximate angular position of a line drawn from the towing craft to the glider. However, the tow line is subject to vibration and slapping due to extraneous forces acting thereon, so the connector 304 is dampened as by dashpots 306 and 301 connected between the connector 304 and the housing 36 I A link 3| is connected between the connector rod 334 and an arm 3|2 of a potentiometer 3|3 to displace the slider according to vertical movements of the connector 304. A similar link 3| 4 is connected to slider 3|5 of potentiometer 3|6 to displace the slider according to lateral movements of the connector 304. A suitable source of voltage, such as battery 3| 8, is connected across the potentiometers 3|3 and 3|6 and has its mid-point connected to a lead 3|9. It will be apparent that the voltages of the sliders 3|2 and 3i5 are of a sense and magnitude relative to the lead 3|9 corresponding to the vertical and lateral displacements of the connector 304 relative to the axis of the housing 30|, which forms the reference axis of the formation.

Potentiometer slider 3|2 is connected by lead 32| in series with a phase detector 323 that is actuated according to pitching movements of the towing craft as determined by pick-offs 324 and 325 of vertical gyro 326. Lead 328 from the other side of the phase detector 323 is connected through the tow line to one side of a phase detector 33|, that is actuated by voltages from the pick-oils and 334 of gyro vertical 335 corresponding to the pitching movements of the glider. Phase detector 33| is connected by lead 336 to control horizontal pointer 331 of the cross pointer indicator 336. The return circuit for the horizontal pointer circuit is through the neutral lead 3|9 in the tow line to the center terminal of battery 3| 8. The circuit of potentiometer slider 3|2, phase detector 323, phase detector 33| and horizontal pointer 331 is a series circuit similar to that described in connection with Fig. 5 for controlling the horizontal pointer in accordance with the difference in pitching angles of the two craft as well as the deviation of the glider relative to the reference axis.

Similarly, the slider 3|5 is connected by lead 34| to phase detector 342 that is actuated in accordance with rolling movements of the towing craft is determined by voltages from pick-ons 344 and 345. The other side of phase detector 342 is connected by lead 346 through the tow line to phase detector 341 that is supplied with voltages corresponding to rolling movements of the glider as determined by pick-offs 349 and 35| of the vertical gyro 15. The phase detector 341 is also connected by lead 352 to the control circuit for horizontal pointer 331, the return path of which is formed by the neutral lead 3|9 through tow line to the central terminal of the battery 3|8. The Vertical pointer 353 is thereby positioned in accordance with the difference in the rolling movements of the towing craft and the glider, as well as the deviation of the glider from a predetermined position relative to the reference axis.

Cross pointer indicator 338 thus has its pointers centrally located when the towing craft and the glider have the same attitude and the glider is in a predetermined position relative to the reference axis of housing 30|. If the glider deviates from this position the potentiometers will produce voltages to move the pointers corresponding to the direction and amount of lateral and vertical deviation. If the towing craft changes its attitude a similar indication will appear, at which time the glider pilot may adjust the attitude of the glider to match that of the towing craft. The use of the voltages corresponding to the difference in attitudes of the two craft compensates 'for errors inithefreferencesaxis.due to .changesin attitude ofi the towing craft.

A simplified arrangement ;of the. system Ashown in, Fig. 11 .iss illustrated. in; Fig. '.12. in .which the glider is suppliedfwith an indication. oftthe vatti- .tude of thev towing craft and its position relative to the reference-axis. This. system does not:.corn pensate for errors in the reference axis dueto changes in theattitude ofthe towing craft. The towing connector 304"actuates..potentiometensliders 3|2 vand 315 in the Vsamemanner asthatde- Vscribed inconnection with-Fig. 11 to provide voltages correspondingto movementsof the tow-line relative to theA reference axis of the. towing craft. These voltages correspond. to .theposition of the gliderrelative to the reference axis. vhevoltage of .slider 312 .is connected `as lay-:lead 35| through the-towline `to the-circuit of horizontal pointer '352 ofv the .cross mpointer indicator y 353. The return of .thehorizontal-pointer circuit is by way of neutral lead 365 through .the .towline to the center point ci the battery SH3. .The voltage of slider 315 is connected by lead Sd through the tow line to the circuit of vertical pointer 365, the return circuit thereof being through neutral. lead 365i. The pointers ofthe'cross'pointer indicator 363 are thereby `positioned in accordance with the position' of the connector'' relative to 'the reference axisof `the housing 313|. Thesevoltages correspond tol the vertical and-lateral displace- 3 ments of the glider relative to the referencejaxis.

A gyro vertical-`367 carriedby the towing craft acts through phase detectors'l! and 359 toapply voltages to horizon repeater indicator S'lll'asrby leads 312 and-313- co-rresponding vto pitchand f'- tice may anticipate'such maneuvers-by observing r the horizon repeater indicator' 31|.

-Three types of.` systems for formation. control have been vdescribed herein and several types of indicating,- as well 'as-automatic Vpilot circuits, have been included. Ilz-should be understoodithat the variousindicating circuits and the. automatic pilot circuits. may be adapted foruse with-any of the three formation control systems.

Each ofthesystemshas a transmitter -Which determines a reference axis for `the formation. Receivers 'carried bythe various craft inthe forl'mation determine the position of the respective craft relative to the reference axis of the transmitters and also determine the attitude of the control craft' which r`carries' the transmitter. vIn addition, some 'of -the indicating circuits andthe automatic lpilctcircuit describedhave compensating means -for' correctingerrors inthe reference axis vduev to'movements of the control craft. rfhis compensa-tionfmayi-be effected either Vby adjusting the position-fof thefreferenceaxis or comparingthe attitudes 'of the lrespective craft. yIn the flatter '-case; thekreceivers 'include means ffor determining..thediiference infthefattitudes of the 'respctive'Jc'r-aft.

-Asmany changes.:could:be. made in the above construction 'andi-.many apparently widely different embodiments of this invention could be made fwithout idepartingLfromthe scope thereof, it is Aintended thatall-matter-contained in the-above descriptionuor shown. inthe-accompanying draw- .ing @shall .che interpreted as .illustrative andnot 1 ing craft,zasignaligenerator:carried by said leadiing:orafteands'responsivetozthe-rpositicn of said towylineforiprdducing :signals corresponding to thefipositio'n :,.ofsaidz-tow lineirelative -to said leading craft, meansrresponsive to said;,device yfor .1 modifying ,said #signals "in accordance .with

.f'movem'entsof-.said leading. craft; and means car- --red:by,=.said: following. craft and responsive vto saidf-signals .forgdeterminingf the; position of said followingicraft relative'toisaidpleading craft.

:52.: In '.af.glideracontrolisystem, a following craft connected.: by ai .tow-flineto.. a leading craft, an

:.attitudefindicatingcdevice.:carried by said lead- -ing z-craft, 1; afttsignaLxgenerator f responsive to .the

position; of said:.towflinel for-f producing a signal .corresponding tontheposition .of said tow line relative to said lleading; ,craftfmeans vresponsive vto saididevice .formodifyingfsaid signal inaccordance with changesfin-iattitude of said leadingu-craft, f:a:.second..1attitude f determining device .carriedxbyaidffollowing craft,..and` means responsivetosaid-signals and said second kdevice 'fortdeterminingithexdiierence in attitude posi- :tions offsaidtvto craft.

L 3. :A;.;:gliderscontrol system' comprising a' .following; craftsconne'ctedaby 4at tow .line to-.a' leadinggcraftpxa signaligenerator responsive.l to. the positionfoffrsaidi;towiline .for. producing signals correspondingatonthe; position of said .tow 'aline relativegtoff saidleading.; craft, an attitude indi- ;catingzdevice:carried'.by said-leading craft for producingosignalscorrespon-dingto the attitude vof. said `'lea-dingecraft; andfme'ans in said .following-craft connectedpto; saidzsignal ygenerator and said attitude devicewfort ascertaining thezattitudesofnsaidleadingeicraft .and fthe :position of .said-foliowingicraft:relativefthereta ,l 4..f:A..g1ider control ."system .comprising .a fol- \lowingncraftfcnnnectectby. aftow line to. a lead- ;ing;.zcraft,1.` afssign'alfgenerator responsive to. the f. position fofrsaid: ytow'. :line :,for producing signals corresponding: toz'ithezposition ,of .said1-tovr :line

relative. 4rtocs'aidf:leading craft,l ari-attitude indicating.;:device-:carried :fby said, leading vcraft for producing.; signals; cor-respending to the attitude of saidfleadingzxcraft, s afsecond k.attitude indicat- :ing .device-carried bic-"said .following craft, .and

means'` connected to .'saidizgenerator and said :devicesfondeterminingzthe differencey in attitude of '.Saidtwoz 'craft'.and :thezpositicn of :said following .craftrelatiyeto'said/leadingxzraft.

.-5..A.r formation.,-.zcontrolsysteml comprising a transmitter.I mountable in: a first craft .producing signals dependent upon angular-deviation from; a, `referencev `axis having a Y.predetermined angular. lrelationship :to: an, :axis fof said craft, an

attitude :indicating :device-for modulating said transmittersignals.` ari-receiver carried -by a'sec- .ond craftrandfiresponsive tosaid transmitter.- a

:craftrrelative tofaidi axis;v and anfindicator re- 19 sponsive to said second device and said receiver for indicating the difference in attitude of said tWo craft.

6. A formation control system comprising a transmitter mountable in a first craft producing signals dependent upon angular deviation from a'reference axis having a predetermined angular relationship to an axis of said craft, an attitude indicating device for modulating said transmitter signals, a receiver carried by a second craft and responsive to said transmitter, a second attitude indicating device carried by said second craft, and an automatic pilot responsive to said receiver and said second device for maintaining said second craft in a predetermined position and relative to said axis, and a predetermined attitude relative to said one craft.

7. In a craft guidance system, generating and transmitting means mountable on a first craft producing signals dependent upon angular deviation from a reference axis having a predetermined angular relationship to an axis of said craft, receiving and reproducing means mountable on a second craft responsive to said signals for determining the deviation of said second Craft from said reference axis, and means for modifying the direction of said signals to compensate for movements of said reference axis caused by attitude changes of said first craft.

8. In a craft guidance system, an attitude indicating device mountable on a first craft and generating impulses, generating and transmitting means mountable on said craft producing signals dependent upon angular deviation from a reference axis having a predetermined angular relationship to an axis of said craft, said signals being altered by said device in accordance with changes in attitude of said first craft to produce resultant signals, receiving and reproducing means mountable in a second craft and responsive to said resultant signals, a second attitude indicating device generating impulses and carried by said second craft, and means responsive to the algebraic sum of the impulses from said devices and to the input of said receiving and reproducing means for determining the difference in the attitudes of said two craft.

9. In a craft guidance system, an attitude indicating device mountable on a first craft and generating impulses, a transmitter mountable on said craft producing signals dependent upon angular deviation from a reference axis having a predetermined angular relationship to an yaxis of said craft, said signals being further altered by said device in accordance with changes in attitude of said first craft to produce resultant signals, a receiver mountable in a second craft and responsive to said resultant signals for ascertaining the position of said reference axis and the attitude of said first craft, an attitude indicating device generating impulses and mountable in said second craft, and means responsive to the algebraic sum of impulses from said devices for modifying the signal input to said receiver to compensate for the difference in the attitudes of said two craft.

10. In a craft flight formation guidance system, an attitude indicating device mountable in a first craft, a transmitter mountable in said first craft producing signals dependent upon angular deviation from a reference axis having a predetermined angular relationship to an axis of said craft, said signals being further altered by said device to produce resultant signals, a second attitude indica-ting device mountable in a second craft, a receiver mountable in a second craft and responsive to said resultant signals, and an indicator actuated by said receiver and said second attitude indicating device for providing a guidance indication on said second craft.

l1. In a craft formation control system, an attitude indicating device mountable in a first craft, a transmitter mountable on said first craft producing signals dependent upon angular deviation from a reference axis having a predetermined relationship to an axis of said craft and actuated by said device to produce signals characterizing attitude changes of said craft, a second attitude indicating device carried by a second craft, a receiver mountable in said second craft responsive to said signals, and an automatic pilot responsive to said signals and said second device for maintaining said second craft in a predetermined position relative to said axis.

12. In a craft guidance system, a transmitter mountable in a craft producing signals dependent upon angular deviation from a reference axis having a predetermined angular relationship to an axis of said craft, a deviation rate device carried by said craft for determining the rate of attitude changes of said craft from a predetermined line of flight, and means responsive to said rate device for positionally modifying said axis to compensate for changing attitude movements of Said craft.

13. In a craft guidance system, a transmitter mountable on a craft producing signals dependent upon angular deviation from a reference axis having a predetermined angular relationship to an axis of said craft, a device carried by said craft for determining the rate of deviation thereof from a straight course, and means responsive to Said device for changing the direction of said signals of said transmitter during course changes of said craft to compensate for such changes.

le. In a craft guidance system, a transmitter mountable on a craft producing signals dependent upon angular deviation from a reference having a predetermined angular relationship to an axis of said craft, and means responsive to the rate of deviation of said craft from a straight course for changing the angular position of said reference axis to compensate for said deviation.

15. A craft guidance system comprising a transmitter mountable on a first craft producing first modulated signals dependent upon angular deviation from a reference axis having a predetermined angular relationship to an axis of said first craft, an attitude indicating device on said first craft for additionally modulating said signals, and a receiver mountable on said second craft and responsive to said first modulated signals for determining the position of said second craft relative to said axis and to said additional modulation for determining the attitude of said first craft.

16. A craft guidance system comprising an attitude indicating device mountable on a first craft, signalling apparatus including a transmitter mountable on said craft producing signals dependent upon angular deviation from a reference axis having a predetermined angular relationship to an axis of said first craft, a receiver carried by a second craft responsive to said signals for determining the deviation of said second craft from said reference axis, and compensating means responsive to said attitude indicating device for changing the angular position of said 21 reference axis to compensate for attitude changes of said first craft.

17. A craft Iguidance system comprising a transmitter mountable in a first craft producing rst modulated signals dependent upon angular deviation from a reference axis having a predetermined angular relationship to an axis of said first craft, an attitude indicating device mountable in said first craft for additionally modulating said transmitter signals, a receiver mountable in a second craft and responsive to said transmitter signals, and indicating means mountable in said second craft and responsive to the input signals of said receiver for indicating both the attitude of said first craft and the position of said second craft relative to said reference axis.

18. A craft flight formation control system comprising a transmitter mountable on a craft producing signals dependent upon angular deviation from a reference axis having a predetermined angular relationship to an axis of said craft, an attitude indicating device mountable in said rst craft for modulating said signals, a receiver carried by a second craft and responsive to said modulated signals, and an automatic pilot responsive to said receiver for maintaining said second craft in a predetermined position relative to said reference axis.

19. A craft guidance system comprising an attitude indicating device mountable in a rst craft, signalling apparatus including a transmitter mountable on a craft producing signals dependent upon angular deviation from a reference axis having a predetermined angular relationship to an axis of said craft, a receiver mountable in a second craft and responsive to said transmitter signals, compensating means responsive to said device for modifying the direction of the output of said signalling apparatus to compensate for changes in attitude of said one craft, and an indicator responsive to said receiver for indicating the position of said second craft relative to said axis.

20. A craft formation control system comprising an attitude indicating device mountable in a first craft, signalling apparatus including a transmitter mountable on an aircraft producing signals dependent upon angular deviation from a reference axis havingI a predetermined angular relationship to an axis of said craft and including a receiver mountable in a second craft and responsive to said transmitter signals, compensating means responsive to said device for changing the output of said signalling apparatus to compensate for changes of attitude of said first craft, and an automatic pilot responsive to said receiver for maintaining said second craft in a predetermined position relative to said reference axis.

2l. A craft iiight formation control system comprising a transmitter mountable on a rst craft, a directional beam antenna coupled thereto emitting symmetrically oriented patterns of radiant energy signals about a reference axis having a predetermined angular relationship to an axis of said craft, an attitude responsive device mountable on said craft, means responsive to said device for modulating said transmitter signals, and a receiver carried by a second craft and responsive to the modulation of said transmitter for determining the position of said second craft relative to said reference axis and for determiningthe attitude of said first craft.

FREDERIC A. JENKS.

REFERENCES CITED The following referenlces are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 541,286 Moore June 18, 1895 1,149,122 Fuller Aug. 3, 1915 1,225,796 Fricke May 15, 1917 1,638,417 Sperry Aug. 9, 1927 1,666,897 Hammond Apr. 24, 1928 1,983,079 Hansen Dec. 4, 1934 1,985,265 Smith Dec. 25, 1934 1,987,680 Henderson Jan. 15, 1935 2,119,530 Dunmore June 7, 1938 2,158,584 Koster May 16, 1939 2,170,835 Simon Aug. 29, 1939 2,176,469 Moueix Oct. 17, 1939 2,257,320 Williams Sept. 30, 1941 21,262,033 Moseley Nov. 11, 1941 2,262,245 Moseley Nov. 11, 1941 2,296,032 Hammond Sept. 15, 1942 2,362,892 Land Nov. 14, 1944 2,396,453 Windle Mar. 12, 1946 2,400,400 Duer May 14, 1946 FOREIGN PATENTS Number Country Date 524,876 Great Britain Aug. 16, 1940 

